Certain subclasses of calcium phosphates, specifically those which comprise specific arrangements of surface microporosity and micro-architecture have been described as being osteoinductive, which term refers to the ability of materials to induce bone cell growth and thus to initiate new bone formation in non-osseous tissue. The formation of such bone includes attachment and aggregation as well as proliferation and differentiation of cells on the material surface, followed by bone matrix formation on the material surface, bone mineralization and bone remodelling to form mature bone. The osteoinductive potential of calcium phosphate materials varies, as indicated by the earliest time for bone formation to occur and the amount of the induced bone.
When an osteoinductive calcium phosphate material is used as in implant material during surgical repair of bone defects, new bone is formed both by osteoconduction near the existing bone as well as by osteoinduction far from the existing bone. Meanwhile the osteoinductive calcium phosphate material would enhance osteoconductive bone formation since it concentrates growth factors and attracts bone-forming cells. Therefore the use of osteoinductive calcium phosphate materials in bone repair results in bone formation starting earlier, in bone formation at increased amounts and in bone formation far from the existing bone as compared to non-osteoinductive calcium phosphate materials. In general, the higher osteoinductive potential of the material, the more effective procedures aimed at repairing bone defects can be performed. Therefore there exists an ongoing need for improving the osteoinductivity of resorbable calcium phosphate materials.